I started my class year with a combination of traditional compasses and a set of slide-and-measure compasses that last year's teacher bought at the end of the year before giving the class to me. I was extremely underwhelmed by their performance. Among the issues:
- The pencil hole would slide while you were tracing an arc, which mostly defeats the purpose of the entire enterprise
- Our workbooks were spiral-bound, and these compasses can only draw an arc if the entire compass can lay flat on the page, frustrating my students to no end
- Being made of plastic, they would fall apart in the students' hands. (It is possible that the other teacher bought particularly cheap models, but it's not clear to me how the device could be made to last given the best intentions.)
I'd buckle in and live with it if stabbings were a frequent event in my classroom. But it simply isn't. And if a student were to stick a compass into a classmate, I would be infinitely more prone to hold the student accountable instead of the compass. As others have noted, the general education environment is full of nigh-equally pointed objects.
If you're dealing with a cohort of students with emotional disabilities, then by all means you should set up your classroom to restrict the ability to cause harm to oneself or others. Barring that, they are a bad solution to a non-existent problem.